Push-pull circuit arrangement for ultra-short waves



Sept. 9, 1947. J. M. VAN HOFWEEGEN Er'AI. 4 1 I PUSH-PULL CIRCUIT ARRANGEMENT FOR ULTRA-SHORT WAVES Filed March 24, 1943 mmzors do/mAm/rs Maw/v0: 14w flarwtzazw 4ND Mx/M/mw Jdl/Mf 07m SrRurr,

Patented Sept. 9, 1947 PUSH-PULL CIRCUIT ARRANGEMENT FOR ULTRA- SHORT WAVES Johannes Marinus van Hofweegen and Maximiliaan Julius Otto Strutt, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application March 24, 1943, Serial No. 480,363 In the Netherlands May 19, 1941 Section 1, Public Law 690, August 8,1946.

Patent expires May 19, 1961 3 Claims.

This movement relates to a circuit arrangement for ultra short waves, in which use is made of a resonant circuit substantially consisting of two juxtaposed and parallel conductors.

To avoid undesired coupling of such a resonant circuit and the other parts of the arrangement, it is known to surround the conductors of the resonant circuit with screening means which are earthed in regard to high frequency currents.

When making use of shielded resonant circuits of the type referred to above in push-pull circuit arrangements, which comprise such a shielded resonant circuit both in the input circuit and in the output circuit, we have found that disturbing oscillation phenomena frequently occur.

According to the invention, this drawback is avoided in push-pull circuit arrangements by taking care that the natural frequency of the system included in the input circuit, constituted by the parallel conductors jointly and the screening means, differs from the natural frequency of the corresponding system included in the output circuit.

The invention will be more fully explained by reference to the accompanying drawing, which represents a push-pull amplifying circuit according thereto.

In the drawing, I and 2 designate push-pull connected amplifying tubes whose control grids 3, 4 are respectively connected to the ends of a resonant circuit 5 consisting of two juxtaposed parallel conductors 5a, 5b and a movable short circuit bridge 50; the anodes 6, 1 are respectively coupled with the end of a resonant circuit 8 included in the output circuit of the arrangement, the last mentioned circuit being constituted by the parallel conductors 8a, 8b and the'short-circuit bridge 80 which is also movable.

Each of the resonant circuits 5 and 8 is surrounded by earthed screening means 9 and [0, respectively, to which one end of the conductors 5a, 5b and 8a, 8b, respectively, is electrically connected. The oscillations to be amplified are supplied, for instance, through the intermediary of a coupling loop H having terminals [2, to the circuit 5 included in the input circuit of the arrangement, and the amplified oscillations may be derived in an analogous manner from the resonant circuit 8 interposed in the output circuit through the intermediary of a coupling loop I3 having terminals [4. As is schematically represented in the drawing, direct current feed voltages are supplied to the electrodes of the tubes 1 and 2; this has not been further illustrated, since it is not essential to the present invention.

In push-pull circuit arrangements of the-type referred to above, undesirable oscillation phenomena may occur which are brought about as follows: The input circuit of the arrangement, as well as the output circuit, comprises the resonant circuit 5 and 8, respectively, and in addition a resonant system constituted by the two parallel conductors 5a, 5b and 8a, 8b jointly, and the envelopes 9 and I0, respectively. In regard to the two last-mentioned systems, the tubes I and 2 are not connected in push-pull but in parallel, as a result of which the mutual conductance of this system is materially higher than that of the push-pull arrangement and oscillation of the ar rangement (for instance due to the control-grid anode capacity) may readily occur in the form of construction represented. The frequency of the oscillations thus produced corresponds to the natural frequency of the resonant systems constituted by the resonant circuit conductors jointly and the screening means associated therewith.

According to the invention, these disturbing phenomena can be avoided by causing the natural freuqency of the system connected in the input circuit and constituted by the conductors 5a, 5b and the screening means 9 to differ from the natural frequency of the corresponding resonant system 8, 8a, 8b and I0 in the output circuit of the push-pull arrangement, which can be achieved in a simple manner, for instance by making the length ii of the shrielding envelope 9 different from the length l2 of the shielding envelope H), the construction and dimensions of the screened resonant circuit included in the input and output circuits being otherwise the same.

To attain the purpose aimed at, it is also possible, of course, to make use of other means known per se for the obtainment of definite tuning of such a resonant system essentially consisting of two parallel conductors. Thus, for example, the electric length of one of the screens, with equal metric length thereof, can be controlled by the interposition of capacities or inductances.

Of course, the invention applies not only to push-pull circuit arrangements for amplifying electrical oscillations but also, .for instance, to push-pull arrangements for producing or mixing electrical oscillations; in the last-mentioned case, for instance, in a superheterodyne receiving set, the resonant circuits constituted by the parallel conductors 5a, 5b and 8, 8a, 8b, will be tuned respectively to the frequency of the local oscillations and the frequency of the incoming oscillations,

What is claimed is:

1. A push-pull circuit arrangement for ultra short waves, in which the input and output circuits each comprise a resonant circuit substantially consisting of two identically dimensioned juxtaposed and parallel conductors surrounded by metallic screening means, and in which the natural frequency of the system included in the input circuit and constituted by the parallel conductors jointly with the screening means is different from the natural frequency of the corresponding system included in the output circuit.

2. An ultra short Wave amplifier system comprising a pair of electron discharge devices each having an input electrode and an output electrode, a tuned lecher Wire circuit coupled to the input electrodes of said devices, and a tuned lecher Wire circuit coupled to the output electrodes of said devices, a shield surrounding each of said tuned lecher wire circuits, each shield being connected to the tuned circuit it surrounds and cooperating therewith to form a resonant system, said shields being sufficiently difierently dimensioned to cause said resonant systems to have different natural frequencies, whereby the occurrence of disturbing parasitics due to interacting between input and output circuits are avoided.

3. An ultra short Wave push-pull system cornallel conductors connected at one end to the 4 control grids of said devices, a short-circuiting slider bridging said conductors, a metallic sleeve-like shield surrounding said parallel conductors for substantially their entire length, a connection from ground to said shield, and another pair of parallel conductors connected at one end to the anodes of said devices, a shortcircuiting slider bridging said last pair of conductors, a metallic sleeve-like shield surrounding said last pair of parallel conductors, and a connection from said last shield to ground, said shields being diiferently dimensioned, whereby the natural frequency of the circuit comprisingthe first mentioned pair of parallel conductors jointly with their surrounding shield is difierent from the natural frequency of the circuit comprising the second mentioned pair of conductors jointly with their surrounding shield.

J O'HANNES MARINUS VAN HOFWEEGEN. MAXIMILIAAN JULIUS OTTO STRUTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,109,843 Kassner Mar. 1, 1938 2,169,305 Tunick Aug. 15, 1939 2,141,242 George et a1. Dec. 27, 1938 2,216,96e Stepp Oct. 8, 1940 2,236,004 lvIacLean Mar. 24, 1941 

